JP3358091B2 - Two-wire electronic switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-wire electronic switch which can be used for either AC or DC.

[0002]

2. Description of the Related Art As a conventional two-wire electronic switch, for example, as disclosed in Japanese Patent Application Laid-Open No. 60-36655, an electronic switch of either an AC two-wire electronic switch or a DC two-wire electronic switch is known. Is used. In an AC two-wire electronic switch, a load and an AC power supply are connected in series to a pair of terminals. A diode bridge is connected between the terminals, and a switching element such as a thyristor and a sensor circuit are connected in parallel with the diode bridge. A capacitor is connected in parallel with the sensor circuit to supply a constant power supply.When the detection circuit is turned on, the thyristor is turned on, power is supplied to the load at a predetermined conduction angle, and the capacitor is charged when the detection circuit is off. Power to the sensor circuit.

In a DC two-wire electronic switch, a constant voltage circuit and a load switching element are connected between a pair of terminals, and a sensor circuit operates by suppressing a voltage fluctuation which fluctuates greatly by the constant voltage circuit. I have.

[0004]

However, such conventional DC two-wire electronic switches are independently manufactured for DC or AC, and cannot be shared.

The present invention has been made in view of such conventional problems, and can be used for both DC and AC without changing the basic circuit of a DC two-wire electronic switch. An object of the present invention is to provide a two-wire electronic switch.

[0006]

SUMMARY OF THE INVENTION The present invention is a two-wire electronic switch in which a load and a power supply are connected in series between first and second terminals, and is connected between the first and second terminals. Having a diode bridge, a switching element for short-circuiting a pair of terminals of a positive terminal and a negative terminal, a sensor circuit for supplying a switching signal to the switching element, and a first constant voltage circuit for supplying a constant voltage to the sensor circuit. A two-wire electronic switch basic circuit, a thyristor connected in series between the positive terminal of the diode bridge and the positive terminal of the DC two-wire electronic switch basic circuit, and a positive terminal and a negative terminal of the diode bridge.
Connected between the thyristor gate and the DC two-wire electron
A second constant voltage circuit for supplying a constant voltage to the switch basic circuit , one end of which is commonly connected between the output terminal of the second constant voltage circuit and the gate of the thyristor, and the other end of which is a DC two-wire electronic switch it is characterized in that it comprises between the positive terminal connected resistors, a.

[0007]

SUMMARY OF] According to the present invention having such a feature, first, when a direct current or power supply and a load of alternating current between the first and second terminals connected in series, is rectified by a diode bridge, the
Power is supplied to the basic circuit of the DC two-wire electronic switch through the constant voltage circuit 2 . When the internal switching element is turned on by the sensor circuit of the DC two-wire electronic switch, the current flowing through the resistor increases and the thyristor is triggered. Thereafter, when the power is AC , the thyristor is turned off at each zero crossing point, but immediately turned on, so that the power is continuously supplied.
When the power source is DC, the thyristor is continuously turned on without repeating turn-on and turn-off at each zero-cross point. When the output of the basic circuit of the DC two-wire electronic switch is turned off, the internal switching element is also turned off, so that the thyristor can be immediately turned off.

[0008]

FIG. 1 is a block diagram showing the overall configuration of a two-wire electronic switch according to one embodiment of the present invention. In this figure, a load 3 and an AC or DC power supply 4 are connected in series between a first terminal 1 and a second terminal 2. Well, this terminal 1,
As shown, a diode bridge 5 is connected between the two, and the anode of the thyristor 6, the drain of the power MOSFET 7, and the resistor R1 are connected to the positive terminal.
The gate terminal of the thyristor 6 is commonly connected to one end of the resistor R2 and the source end of the power MOSFET 7, and further connected to the gate terminal of the FET 7 via the Zener diode 8. The other end of the resistor R1 is connected to the gate terminal of the FET 7, and further connected to the negative terminal of the diode bridge 5 via the Zener diode 9. This power MOSFET 7
Has a withstand voltage corresponding to the power supply voltage. For example, when a commercial AC power supply is connected, it has a withstand voltage of several hundred volts. The FET 7, the resistor R1, and the Zener diode 9 constitute a second constant voltage circuit.
The Zener diode 8 is a protection diode for the power MOSFET 7.

The common connection terminal between the cathode of the thyristor 6 and the resistor R2 is connected to the positive terminal 10a of the basic circuit 10 of a normal DC two-wire electronic switch. The basic circuit 10 includes a transistor 11, which is a switching element, a first constant voltage circuit 12, and a sensor circuit 1 as shown in FIG.
3 is included. The sensor circuit 13 includes, for example, an oscillation circuit, a detection circuit for detecting a decrease in oscillation amplitude, a comparison circuit, and the like, and supplies a switch signal to the transistor 11. The negative terminal 10b of the basic circuit 10 of the DC two-wire electronic switch is connected to the negative terminal of the diode bridge 5 and the anode terminal of the Zener diode 9 constituting the constant voltage circuit.

Next, the operation of this embodiment will be described. For example, when an AC power supply is connected as the power supply 4, the voltage at the positive terminal A with respect to the negative terminal G of the diode bridge 5 is subjected to full-wave rectification, and changes as shown in FIG. This voltage becomes a constant voltage substantially determined by the Zener diode 9, and a pulsating voltage as shown in FIG. 2B is supplied to the basic circuit 10 of the DC two-wire electronic switch via the power MOSFET 7 and the resistor R2. You. As a result, a substantially DC voltage is also supplied to the basic circuit 10 of the DC two-wire electronic switch. Since the constant voltage circuit 12 is provided in the basic circuit 10 of the DC two-wire electronic switch, the voltage is further stabilized in the basic circuit 10 to a predetermined voltage and applied to the sensor circuit 13. Note that the period T1 indicates a state where the object is not approaching.

In a period T2 in which an object or the like approaches the vicinity of the sensor circuit 13, the object is detected by the sensor circuit 13 and a switch signal is given to the transistor 11.
Therefore, the switch 11 is turned on and a current flows through the resistor R2. When the voltage drop of the resistor R2 increases, the thyristor 6 is triggered, and the load current of the load 3 flows through the diode bridge 5, the thyristor 6, and the switching transistor 11 in the basic circuit 10. The voltage between the gate of the thyristor 6 and the positive terminal of the DC two-wire basic circuit 10 increases, and the thyristor 6 is turned off at each zero cross. However, the voltage increases and the voltage of the resistor R2 increases. It turns on immediately after the zero cross.

When the object moves away from the sensor circuit 13, the output from the sensor circuit 13 stops and the transistor 11 is turned off. Therefore, the thyristor 6 is immediately turned off before reaching the zero crossing point, that is, before the holding current becomes lower. Therefore, the time until the turn-off is shortened as compared with the conventional AC two-wire electronic switch, and the responsiveness can be improved. Also, when a DC power supply is connected as the power supply 4, a constant voltage is supplied to the positive terminal of the diode bridge 5 instead of a pulsating flow as shown in FIG. Is exactly the same as when an AC power supply is connected. Therefore, any of an AC power supply and a DC power supply can be used as the power supply 4.

[0013]

As described in detail above, according to the present invention, the basic circuit of a DC two-wire electronic switch is used as it is, and an additional circuit is connected thereto, so that both the DC and AC power supplies can be powered. It can be a two-wire electronic switch for both AC and DC that can be connected as. The basic circuit of a DC two-wire electronic switch is usually IC
Therefore, the configuration can be made by connecting a few additional circuits without changing the IC circuit itself. In addition, a switching element is provided in the basic circuit of the DC two-wire electronic switch, and when the element is turned off, it is turned on immediately, so that the response of the electronic switch can be improved even when an AC power supply is used. Is also obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a two-wire electronic switch according to one embodiment of the present invention.

FIG. 2 is a time chart illustrating the operation of the present embodiment.

[Explanation of symbols]

 1, 2 terminal 3 load 4 power supply 5 diode bridge 6 thyristor 7 power MOSFET 8, 9 Zener diode 10 DC two-wire electronic switch basic circuit 11 transistor 12 constant voltage circuit 13 sensor circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-253314 (JP, A) JP-A-64-89814 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03K 17/945

Claims (2)

(57) [Claims] 1. A two-wire electronic switch in which a load and a power supply are connected in series between first and second terminals, comprising: a diode bridge connected between the first and second terminals; Basic two-wire DC electronic switch having a switching element for short-circuiting a pair of terminals at the positive and negative ends, a sensor circuit for supplying a switch signal to the switching element, and a first constant voltage circuit for supplying a constant voltage to the sensor circuit A thyristor connected in series between a positive terminal of the diode bridge and a positive terminal of the basic circuit of the DC two-wire electronic switch; and a thyristor connected between the positive terminal and the negative terminal of the diode bridge.
The thyristor gate and the DC two-wire electronic switch.
A second constant voltage circuit for supplying a constant voltage to the switch basic circuit , one end of which is commonly connected between the output terminal of the second constant voltage circuit and the gate of the thyristor, and the other end of which is the DC two-wire. two-wire electronic switch, characterized by comprising: a positive terminal connected resistors of formula electronic switch, the. 2. The power supply according to claim 2, wherein the second constant voltage circuit is a power MOS.
2. The two-wire electronic switch according to claim 1, comprising an FET and a Zener diode for stabilizing the gate voltage.